Instrument of precision



(No Model.)

' L. N. JACKMAN;

YIBTS'I'RULJENSI? 01?l PRECISION. No. 283,346. Patented Aug. 14, 1883.

N. Pam. waning. D. c

UNITED STATES PATENT Ormea,

LEMUEL n. y ACKMAN, on nLGiN, iLLinois.

INSTRUMENT F PRECISION.

SPECIFICATION forming part of Letters Patent No. 283,346,^dated August 14, 1883. Application meu April 11,1883. (no model.) Y u To all whom, t may concern Beit known that l', LEMUEL N. JncKMA-N, of Elgin, in the county of Kane and in the State 'of lllinois, have invented certain new and useful Improvements in Instruments of Precision,

and l do hereby declare that the following is a i'ull, clear, and exact description thereof, reference being had to the accompanping drawings, making apart of this specification, inv

whichl Figure l is a perspective view of my gage as arranged for use. Fig. 2 is a like view, en-

larged, of the portioncontaining the adjustabe easily and accurately adjusted when new,

or when fromuse they have become inaccurate; and to this end said invention consists in an instrument of precision provided with ascale,

oi' which each division is separately adjustable, substantially as and for the purpose hereinafter specified.

wVhile my invention is applicable to all instruments of precision, it will sufficiently lustrate its principle and advantages to show its use in connection with one form of such instruments-a j ewel-gage- In the annexed drawings, A represents a round stock or handle, being about the size of an ordinary lead-pencil, and provided with an axial opening, c, that extends from one end nearly to the opposite end of the same.

W'ithin the opening a is loosely tted a round bar, B, which at one end is provided with a round tapering needle, b, that is formed of hardened steel, has a length of about one and one-half inches, and passes outward through a metal box, c', which is secured upon the end of the stockla and reduces said opening a at such point to a size suiiicient only to permit of the free longitudinal movement of said needle. In rear of the bar B is placed a spiral spring, (l, which operates to hold the former with a light yielding pressure at the opposite limit oi' its motion against the box a', with the' needle b projecting from said bon, while a stud, b', projecting from said bar radially through a longitudinal slot, c2, formed in one side of the stock A, acts as a pointer to indicate upon a suitable scale, secured to or formed upon said stock adjacent to said slot, the relative position of said bar and the distance to which the same and said needle have been moved inward from their normal positions. The taper of the needle b is such as maybe necessary in order that pivot-j ewels for watches having certain sizes of openings may be placed upon the same, the jewel having the smallest opening being able to pass but slightly beyond the point, while those having the largest openings will pass nearly to the boi: c.

In use of the instrument each jewel to be gaged is placed upon the needle b and moved over the same un til`it reaches a point when the latter just fills the opening of the former, after which said needle will be moved inward until said jewel impinges upon the box a and further motion in such direction is arrested. The operative now notes the position of the indicator b with reference to the scale, and, removing the jewel, places-the same in a receptacle designated by the number thus indicated.

Y It will be readily seen that while the instrument is in perfect condition its indicated measurement will be accurate and reliable; but experience has shown that after a few days7 use the needle becomes sufficiently worn in places to render untruthful tlre indicated size of jewel-openings, and it has .heretofore Ybeen customary to construct a new scale corresponding to the worn condition of the needle, in order that the instrument might be once more capable of perfect work. lThe time and labor required for such readjustments of the instrument have caused it to be used after number to the desired divisions of" the scale, and, in fact, form a scale for use in connection with the indicator b. For convenience every IOO fifth disk 4engages with and carries along,` a metal plate, E, which bears a suitable number, and the Whole is covered by a plate, F, that is provided With openings through which said disks d and numbered plates E may be observed.

When it is now desiredv to test and adjust the instrument, standard jewels are placed upon the needle and the position of the indicatornoted, and if, as is certain to be true, the Wear of some portion of the said needle causes the scale to be incorrect, the disks d areturned until they coincide once more with the indicator. rlhis operation requires so little time as to render practicable a daily readj ustrnent of the instrument, and, thereby, the perfectly accurate classification ofthe jewels.

Having` thus fully set forth the nature and merits of my invention, what I claim as new is* An instrument of precision provided With a scale, of which'eaeh division is separately adjustable, substantially as and for the purpose specified.

In testimony that I claim the foregoing I 25 have hereunto set my hand this 4th day of April, 1883.

LEMUEL N. JACKMAN.

Vitnesses:

GEO. HUNTER, W. H. GLOUDMAN. 

